Question:
Which of the following is true?
Which of the following is true?
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Three statements name the wrong enzyme or wrong inhibition type; find the antidote concept that holds.
Updated On: Jun 24, 2026
- Acetylcholinesterase inhibition by malathion can be reversed by increasing the level of atropine
- Sulphonamide inhibits folate reductase irreversibly
- Fluoroacetate competitively inhibits aconitase
- Ethanol acts by inhibiting aldehyde dehydrogenase when used in methanol poisoning
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The Correct Option is D
Solution and Explanation
Step 1: Test option A. Malathion is an organophosphate that inhibits acetylcholinesterase. Atropine blocks muscarinic receptors and treats symptoms, but it does NOT reverse the enzyme inhibition itself; that requires an oxime like pralidoxime. So A is false.
Step 2: Test option B. Sulphonamides inhibit dihydropteroate synthase (they are PABA analogues), not folate reductase; dihydrofolate reductase is the target of trimethoprim and methotrexate. So B is false.
Step 3: Test option C. Fluoroacetate is converted to fluorocitrate, which inhibits aconitase, but this inhibition is essentially irreversible/lethal-synthesis type, not a simple competitive block. So C is false as stated.
Step 4: Test option D. In methanol poisoning the toxicity comes from formaldehyde and formic acid generated by alcohol dehydrogenase acting on methanol. Ethanol is given as the classic antidote because it competes with methanol for this enzyme, slowing toxic metabolite formation. By process of elimination D is the intended true answer.
Step 5: Note the wording issue. Strictly, ethanol competes at alcohol dehydrogenase, not aldehyde dehydrogenase as printed. Despite this imprecise wording, D is still the only option that captures the correct antidotal principle and remains the best answer; the other three are clearly wrong.
Answer: Option D.
Step 2: Test option B. Sulphonamides inhibit dihydropteroate synthase (they are PABA analogues), not folate reductase; dihydrofolate reductase is the target of trimethoprim and methotrexate. So B is false.
Step 3: Test option C. Fluoroacetate is converted to fluorocitrate, which inhibits aconitase, but this inhibition is essentially irreversible/lethal-synthesis type, not a simple competitive block. So C is false as stated.
Step 4: Test option D. In methanol poisoning the toxicity comes from formaldehyde and formic acid generated by alcohol dehydrogenase acting on methanol. Ethanol is given as the classic antidote because it competes with methanol for this enzyme, slowing toxic metabolite formation. By process of elimination D is the intended true answer.
Step 5: Note the wording issue. Strictly, ethanol competes at alcohol dehydrogenase, not aldehyde dehydrogenase as printed. Despite this imprecise wording, D is still the only option that captures the correct antidotal principle and remains the best answer; the other three are clearly wrong.
Answer: Option D.
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